Hitherto, a radiation image such as an X-ray image is widely applied for diagnosing in medical field. Particularly, an intensifying screen-film radiation image forming system is still used in the medical field of the world as an image taking system having high reliance and superior cost performance as a result of improvement in sensitivity and image quality in long history of the system. Recently, a digital radiation image detecting device, typically computed radiography (CR) and a flat panel radiation detector (FPD), has been realized and it has been made possible to take a radiation image in a form of digital information and to freely treat or instantaneously transmit the information.
In the CR and FPD, a phosphor plate is provided, which emits light when that is irradiated by radiation, and the luminance of the light emitted by the phosphor plate is an important factor for obtaining a clear radiation image. The CR has a stimulable phosphor plate as the phosphor plate.
The CR has a stimulable phosphor plate as a phosphor plate. The stimulable phosphor plate is a plate which accumulates radiation permeated through a subject and emits light corresponding to the amount of accumulates radiation when the plate is irradiated by exciting light. The plate is constituted by a phosphor layer provided on a substrate. It has been known regarding the stimulable phosphor plate that columnar crystals are formed on the substrate and the luminance of the emitted light is raised when cesium bromide displaying high conversion efficiency of from radiation to light is deposited on the substrate by vapor deposition for forming the phosphor layer. Particularly, in the techniques described in Patent Document 1, it is planed to raise the luminance of the emitted light of the plate by heating the substrate on which the phosphor layer is formed for removing moisture from the crystals of the phosphor layer in addition to the vapor deposition of the cesium bromide onto the substrate.
On the other hand, the FPD has a scintillator plate as the phosphor plate. The scintillator plate is a plate which instantaneously emits light corresponding to the radiation permeated through a subject without irradiation of the exciting light. The scintillator plate is constituted by a phosphor layer provided on a substrate similarly to the above stimulable phosphor plate. As to the scintillator plate, it has been known that the luminance of emitted light is improved when the phosphor layer cesium iodide having high conversion efficiency of from radiation to stimulated light is formed vapor depositing so as to columnar crystals are formed on the substrate. Particularly, in Patent Document 2, the luminance of emitted light is increase by simultaneously spattering an activator such as indium together with the vapor deposition of cesium iodide on to the substrate.
Patent Document 1: Japanese published unexamined application (JP-A) 2003-279696, (paragraphs 0034 to 0035)
Patent Document 2: JP-A 2001-59899, (paragraph 0041)
The phosphor layer is insufficient in the light emission efficiency and space to be improved remains as to the phosphor layer even when the phosphor layer is constituted by cesium bromide or cesium bromide having high conversion efficiency of from radiation to stimulated light or the phosphor layer is improved by techniques such as those described in Patent Documents 1 and 2.
An object of the invention is to provide a producing method of phosphor plate by which the luminance of emitted light can be further improved and a phosphor plate produced by such the method.